Pope Francis is flanked by Ortodox Primate of the Metropolis of Italy Gennadios Zervos, left, and the representative of the Archbishop of Canterbury to the Holy See David Moxon, at the end of the second Vespers prayer in St. Paul Outside the Walls Basilica on the occasion of the liturgical Feast of the Conversion of St. Paul the Apostle, in Rome, Monday, Jan. 25, 2016. (AP Photo/Andrew Medichini)

ABOARD THE PAPAL PLANE (AP) – The pope has something to say about Donald Trump, calling him “not Christian” if the Republican presidential front-runner wants to address illegal immigration only by building a wall along the U.S.-Mexico border.

Trump, who’s a Presbyterian, said, “For a religious leader to question a person’s faith is disgraceful.”